I all my previous years brewing fermentation temp control was not and issue for me, as I had a dedicated fermentation chamber. I never gave it a second thought. Set the thermostat at 63° and didn’t look back. Since I got back in the brewing game here at my new condo, I’ve fermented in the downstairs 1/2 bath. I closed the heat vent off and stayed at a consistent 65° in the winter. Summer is here now. Sunday I brewed Chocolate Starfish porter, with US-04 at an SG of 1.052. Not thinking twice about temperature, I put it in my bathroom and let it go. Today… I’m at 1.013!!! The chocolate is there along with all the other nice flavors I wanted but so are the fussels. Will they fade over time?
They might mellow a bit, but will probably stick around overall (sadly). I had an issue with a recent IPA, where my temperature control got disconnected by accident for <24 hours, and the resulting fusels held on for the entire keg. 
I think it could depend on the yeast. I’ve had some fusels come off Belgian yeast that then did “age out” but it took a long while, almost a year for one batch, about 6 months for another. I’m sorry that I can’t tell you how that will go with US-04, never used that yeast. I have no form of temp control and thankfully the only time I’ve had that problem was with Belgians, and they are supposed to age some anyway.
Hopefully it fades!
With the various English ale dry yeasts I’ve used over the years (e.g., Nottingham, US-04, etc.), the fusels tend to mellow but are still there.
On the other hand, I would encourage weazeltoe to age this a month or two and see what happens. A porter is robust enough that it can stand up to many off flavors.
Fusels will often age into esters. Keep your fingers crossed.
Fusels can break down into esters with time. The high ferm temp saisons that I prefer to bottle show fusels and excessive heat at first but become deliciously complex as they age.
For sure. Even before the screw up I planned on a good two month secondary. I’m really hoping it will fade. I’ve also used US-04 in all my porters and it’s always treated me well. Fingers crossed.
I had the same problem with a saison I brewed last year. It was a big fusel bomb. I kept it outside in the hot, then cool, then cold, and now warm weather and served it a few weeks ago. People were impressed. Said it was a lovely barleywinelike saison.
I’m OK with that.
Christophe